1. Field of Invention
The present invention relates to a radio frequency integrated circuits. More particularly, the present invention relates to a three dimensional (3D) transformer.
2. Description of Related Art
In recent years, the demand for radio frequency integrated circuits has increased significantly due the popularity and convenience of wireless communication. In the design of complementary metal oxide semiconductor (CMOS) radio frequency integrated circuits, the inductor is a very important device to be considered asides from controlling the high frequency property of the active device. Since a CMOS substrate is a highly consumed substrate, managing the property of the inductor is difficult. In the conventional CMOS radio frequency integrated circuits, the inductor is configured on the planar structure of the GaAs circuit. The area of the planar structure of the GaAs circuit is large; thus, the area of the radio frequency integrated circuits becomes correspondingly large and the cost is ultimately increased.
The transformer is also a relevant device in the radio frequency integrated circuits. Many recent studies have focused on replacing the inductor with a transformer Not only such layout can better preserve the chip area, a low consumption of voltage can be achieved. Along with the miniaturization the micromation of devices, the traditional planar type of transformer, which occupies a large area, fails to conform to current demands.